While unsure why the association exists, researchers say that meteorological effects on persistent organic pollutants, such as some pesticides and industrial by-products, may be to blame.
The current explanation for the spatial pattern of prostate cancer is low vitamin D levels in individuals living at northerly latitudes. But the authors of the new study contend that this hypothesis doesn't fully explain the higher incidence of the disease.
"We found that colder weather, and low rainfall, were strongly correlated with prostate cancer. Although we can't say exactly why this correlation exists, the trends are consistent with what we would expect given the effects of climate on the deposition, absorption, and degradation of persistent organic pollutants including pesticides," said Idaho State University researchers Sophie St-Hilaire.
Researchers say the association remained even after controlling for shortwave radiation, age, race, snowfall, premature mortality from heart disease and unemployment.
Approximately one in six men will develop prostate cancer in their life-time, and across the northern hemisphere it has been reported that incidences are higher in the north than the south. Some persistent organic pollutants are know to cause cancer and researchers believe that cold weather slows their degradation, while also causing them to precipitate towards the ground.
Rain and humidity also play important roles in their absorption and degradation. According to St-Hilaire, "this study provides an additional hypothesis for the north-south distribution of prostate cancer, which builds on the existing supposition that individuals at northern latitudes may be deficient in Vitamin D due to low exposure to UV radiation during the winter months. Our study suggests that in addition to vitamin D deficiency associated with exposure to UV radiation, other meteorological conditions may also significantly affect the incidence of prostate cancer."
Citation: St-Hilaire et al., 'Correlations between meteorological parameters and prostate cancer', International Journal of Health Geographics, April 2010, 9(19); doi:10.1186/1476-072X-9-19
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